// private property
const _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
// private method for UTF-8 encoding
const utf8Encode = function (string) {
  string = string.replace(/\r\n/g, '\n')
  let utftext = ''
  for (let n = 0; n < string.length; n++) {
    let c = string.charCodeAt(n)
    if (c < 128) {
      utftext += String.fromCharCode(c)
    } else if ((c > 127) && (c < 2048)) {
      utftext += String.fromCharCode((c >> 6) | 192)
      utftext += String.fromCharCode((c & 63) | 128)
    } else {
      utftext += String.fromCharCode((c >> 12) | 224)
      utftext += String.fromCharCode(((c >> 6) & 63) | 128)
      utftext += String.fromCharCode((c & 63) | 128)
    }
  }
  return utftext
}

// private method for UTF-8 decoding
const utf8Decode = function (utftext) {
  let string = ''
  let i = 0
  while (i < utftext.length) {
    let c = utftext.charCodeAt(i)
    if (c < 128) {
      string += String.fromCharCode(c)
      i++
    } else if ((c > 191) && (c < 224)) {
      let c2 = utftext.charCodeAt(i + 1)
      string += String.fromCharCode(((c & 31) << 6) | (c2 & 63))
      i += 2
    } else {
      let c2 = utftext.charCodeAt(i + 1)
      let c3 = utftext.charCodeAt(i + 2)
      string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63))
      i += 3
    }
  }
  return string
}
const Base64 = {
  // public method for encoding
  encode(input) {
    var output = ''
    var chr1, chr2, chr3, enc1, enc2, enc3, enc4
    var i = 0
    input = utf8Encode(input)
    while (i < input.length) {
      chr1 = input.charCodeAt(i++)
      chr2 = input.charCodeAt(i++)
      chr3 = input.charCodeAt(i++)
      enc1 = chr1 >> 2
      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4)
      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6)
      enc4 = chr3 & 63
      if (isNaN(chr2)) {
        enc3 = enc4 = 64
      } else if (isNaN(chr3)) {
        enc4 = 64
      }
      output = output +
        _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
        _keyStr.charAt(enc3) + _keyStr.charAt(enc4)
    }
    return output
  },

  // public method for decoding
  decode(input) {
    var output = ''
    var chr1, chr2, chr3
    var enc1, enc2, enc3, enc4
    var i = 0
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '')
    while (i < input.length) {
      enc1 = _keyStr.indexOf(input.charAt(i++))
      enc2 = _keyStr.indexOf(input.charAt(i++))
      enc3 = _keyStr.indexOf(input.charAt(i++))
      enc4 = _keyStr.indexOf(input.charAt(i++))
      chr1 = (enc1 << 2) | (enc2 >> 4)
      chr2 = ((enc2 & 15) << 4) | (enc3 >> 2)
      chr3 = ((enc3 & 3) << 6) | enc4
      output = output + String.fromCharCode(chr1)
      if (enc3 !== 64) {
        output = output + String.fromCharCode(chr2)
      }
      if (enc4 !== 64) {
        output = output + String.fromCharCode(chr3)
      }
    }
    output = utf8Decode(output)
    return output
  }
}
export default Base64
